The formulation of laundry detergents and other cleaning compositions presents a considerable challenge, since modem compositions are required to remove a variety of soils and stains from diverse substrates. Thus, laundry detergents, hard surface cleaners, shampoos and other personal cleansing compositions, hand dishwashing detergents and detergent compositions suitable for use in automatic dishwashers, and the like, all require the proper selection and combination of ingredients in order to function effectively. In general, such detergent compositions will contain one or more types of surfactants which are designed to loosen and remove soils and stains. However, the removal of body soils, greasy/oily soils and certain food stains quickly and efficiently can be problematic. Indeed, while some surfactants and surfactant combinations exhibit optimal performance on certain types of soils and stains, they can actually diminish performance on other soils. For example, surfactants which remove greasy/oily soils from fabrics can sometimes be sub-optimal for removing particulate soils, such as clay. While a review of the literature would seem to indicate that a wide selection of surfactants and surfactant combinations is available to the detergent manufacturer, the reality is that many such ingredients are specialty chemicals which are not suitable in low unit cost items such as home-use laundry detergents. The fact remains that most such home-use products such as laundry detergents still mainly comprise one or more of the conventional ethoxylated nonionic and/or sulfated or sulfonated anionic surfactants, presumably due to economic considerations and the need to formulate compositions which function reasonably well with a variety of soils and stains and a variety of fabrics.
Accordingly, there is a continuing search for improvements in detergents, especially laundry and dishwashing detergents and hard surface cleaners. However, the challenge to the detergent manufacturer seeking improved performance has been increased by various factors. For example, some non-biodegradable ingredients have fallen into disfavor. Effective phosphate builders have been banned by legislation in many countries. Costs associated with certain classes of surfactants have impacted their use. As a result, the manufacturer is somewhat more limited than the literature would suggest in the selection of effective, yet affordable, ingredients. Still, the consumer has come to expect high quality and high performance in such compositions even when conducting cleaning operations under sub-optimal conditions, e.g., laundering fabrics in cool or cold water.
The literature does suggest that various nitrogen-containing surfactants would be useful in a variety of cleaning compositions. Such materials, typically in the form of amino-, amido-, or quaternary ammonium or imidazolinium compounds, are often designed for specialty use. For example, various amino and quaternary ammonium surfactants have been suggested for use in shampoo compositions and are said to provide cosmetic benefits to hair. Other nitrogen-containing surfactants are used in some laundry detergents to provide a fabric softening and anti-static benefit. For the most part, however, the commercial use of such materials is rather limited, and the aforementioned nonionic and anionic surfactants remain the major surfactant components in today's laundry compositions.
It has now been discovered that certain alkoxylated quaternary ammonium (AQA) compounds can be used in various detergent compositions to boost performance. Importantly, it has further been discovered that low levels of these AQA compounds provide superior cleaning performance when used in certain combinations with otherwise known or conventional ingredients. Thus, the present invention provides an improvement in cleaning performance without the need to develop new, expensive surfactant species.
Moreover, the AQA surfactants used in the present manner provide substantial advantages to the formulator over cationic surfactants known heretofore. For example, the AQA surfactants herein are compatible with the preferred alkyl sulfate and alkyl benzene sulfonate detersive surfactants. Moreover, the AQA surfactants are formulatable over a broad pH range from 5 to 12. The AQA surfactants can be prepared as 30% (wt.) solutions which are pumpable, and therefore easy to handle in a manufacturing plant. AQA surfactants with degrees of ethoxylation above 5 are sometimes in a liquid form and can be provided as 100% neat materials. In addition to their handling properties, the ability of the AQA surfactants herein to be provided as high concentrate solutions provides a substantial economic advantage in transportation costs. The AQA surfactants are also compatible with various perfume ingredients, unlike other quats known in the art.
In addition to the foregoing advantages, the AQA surfactants herein appear to minimize or eliminate redeposition of fatty acids/oily materials present in an aqueous laundry liquor back onto fabrics which have been previously soiled with body soils. Accordingly, the AQA surfactants herein have now been found to prevent the redeposition of polar lipids from an aqueous laundry bath back onto fabrics from whence body soils have been removed through the laundering process. Stated otherwise, in a laundering liquor, the AQA surfactants herein remove such polar lipids and keep them suspended in the aqueous medium, rather than allowing them to redeposit onto the cleaned fabrics.
In addition to the foregoing qualities, the AQA surfactants herein are surprisingly compatible with the polyanionic materials such as polyacrylates and acrylate/maleate copolymers which are used to provide a builder and/or dispersant function with many conventional detersive surfactants.
Other advantages for the AQA surfactants herein include their ability to enhance enzymatic cleaning and fabric care performance in a laundering liquor. While not intending to be limited by theory, it is speculated that enzymes may be partially denatured by conventional anionic surfactants. It is further speculated that the AQA surfactants herein somehow interact with the anionic surfactants to inhibit that degradation. An alternate theory would suggest that, even when enzymes are used to degrade soils and stains, the degraded residues must be removed from the fabric surface. It may be speculated that the improved detersive performance embodied in the mixture of AQA and anionic surfactants herein simply does a better job in removing these residues from the fabric surface.
In addition to the foregoing advantages, the AQA surfactants herein provide substantial cleaning enhancement with respect to clay soil removal from fabrics, as compared with conventional detergent mixtures. Again, while not intending to be limited by theory, it may be speculated that conventional cationic surfactants associate with the clay in "close-packed" fashion and render the clay more difficult to remove. In contrast, the alkoxylated AQA surfactants are believed to provide more open associations with clays, which are then more readily removed from fabric surfaces. Whatever the reason, the compositions herein containing the AQA surfactants provide improved performance over conventional cationic surfactants with special regard to clay soil removal.
Still further advantages for the AQA surfactants herein have been discovered. For example, in bleaching compositions which comprise a bleach activator (as disclosed herein) it appears that some sort of ion pair or other associative complex is formed with the per-acid released from the activator. It may be speculated that this ion pair is carried more efficiently into the soil as a new, more hydrophobic agent, thereby enhancing bleach performance associated with the use of bleach activators such as nonanoyloxy benzene sulfonate (NOBS). Quite low levels (as low as 3 ppm in the laundering liquor) of AQA surfactants gives rise to these results.
Moreover, in compositions without bleach, the formulator my choose to use somewhat higher levels of AQA to provide enhanced performance benefits. These benefits may be associated with the ability of the AQA surfactants herein to modify the solution characteristics of conventional anionic surfactants such as alkyl sulfates or alkyl benzene sulfonates to allow more of the surfactants to be available to perform their cleaning function. This is particularly true in situations faced by the formulator where the detergent composition is "underbuilt" with respect to calcium and/or magnesium water hardness ions. Under such circumstances, it is preferred to use sufficient AQA surfactant to provide from about 10 ppm to about 50 ppm of the AQA surfactants in the wash liquor. This translates into compositional usage ranges from about 1% to about 5%, by weight, in fully-formulated detergent compositions. (This concentration can vary with product usage rates and the amount of other surfactant present in the wash liquor. For high product concentrations up to about 3500 ppm, the AQA level may be as high as 100-150 ppm in solution. This still only translates to 3-4% AQA surfactant in the finished detergent composition.) It has further been discovered that the AQA surfactants herein containing about 2 ethylene oxide (EO) groups perform extremely well under circumstances of low water hardness or when well-built detergent compositions are used. However, under circumstances of high hardness (about 170 ppm calcium carbonate, and higher) it is more preferred to use AQA surfactants with at least about 3.5 EO groups. Moreover, for some soils and stains, such as fecal matter, AQA surfactants having on the order of 10-20 EO groups are preferred. Accordingly, mixtures of AQA surfactants can be blended and used to provide a broad spectrum of cleaning performance over a wide variety of soils and stains and under a wide range of usage conditions. Representative, but non-limiting, examples of such combinations of AQA surfactants are disclosed in the Examples hereinafter.
Various other advantages of the AQA surfactants over cationic surfactants known in the art are described in more detail hereinafter. As will be seen from the disclosures herein, the AQA surfactants, used in the manner of the present invention, successfully address many of the problems associated with the formulation of modem, high-performance detergent compositions. In particular, the AQA surfactants allow the formulation of effective laundry compositions which can be used to remove a wide variety of soils and stains under a wide spectrum of usage conditions.
These and other advantages of the present invention will be seen from the following disclosures.